Induction of a Ferroelectric SC* Liquid Crystal Phase by an Atropisomeric Dopant Derived from 4,4‘-Dihydroxy-2,2‘-dimethyl-6,6‘-dinitrobiphenyl

Abstract

We report the induction of a ferroelectric SC* phase in two SC liquid crystal hosts using a novel chiral dopant (−)-1 that incorporates an atropisomeric core derived from 4,4‘-dihydroxy-2,2‘-dimethyl-6,6‘-dinitrobiphenyl. The racemic dopant was synthesized in 11 steps with an overall yield of 9% and resolved by chiral stationary phase HPLC in optically pure form. The magnitude and sign of the spontaneous polarization (PS) induced by (−)-1 were found to depend strongly on the nature of the SC host. In a cyclohexanecarbonitrile host, (−)-1 induces a positive polarization that is measurable over the dopant mole fraction range 0.02 < xd < 0.044; in a phenyl benzoate host, (−)-1 induces a negative polarization that falls below detection limit at xd ≤ 0.05. The polarization power (δp) of (−)-1 in the cyclohexanecarbonitrile host is +170 nC/cm2, which is more than eight times that estimated as upper limit in the phenyl benzoate host. These results are rationalized on the basis of the Boulder model for the molecu...